Method of controlling the quality of sintered products



May 12, 1964 H. A. CARLSEN 3,133,131

METHOD OF CONTROLLING THE QUALITY OF SINTERED PRODUCTS 4 Sheets-Sheet 1 Filed March 6, 1962 FIG.1

ATTORNEYS y 12, 1964 H. A. CARLSEN 3,133,131

METHOD OF CONTROLLING THE QUALITY OF SINTERED PRODUCTS Filed March 6, 1962 4 Sheets-Sheet 2 FIG. 4

. 4 m 2%? Q gm;

ATTORNEYS y 12, 1964 H. A. CARLSEN 3,133,131

METHOD OF CONTROLLING THE QUALITY OF SINTERED PRODUCTS 4 Sheets-Sheet 3 Filed March 6, 1962 FIG. 12

Time (Hours) y 1964 H. A. CARLSEN 3,133,131

METHOD OF CONTROLLING THE QUALITY OF SINTERED PRODUCTS Filed March 6, 1962 4 Sheets-Sheet 4 FIG. I4

IN ENTOR.

g v /c 5m QMZMM 72 41 4% United States Patent 3,133,131 METHOD OF CONTROLLING TIE QUALITY OF SINTERED PRODUCTS Henrik A. Carlson, Copenhagen-Valby, Denmark, assignor to F. L. Smidth & 60., New York, N.Y., a corporation of Delaware Filed Mar. 6, 1962, Ser. No. 177,794 20 Claims. (Cl. 26352) This invention relates to the sintering of materials to produce products, which vary in porosity in accordance with variations in the sintering process. More particularly, the invention is concerned with a novel method of controlling the degree, to which a material is sintered in a rotary kiln or like apparatus, in order that the material may not be either overburned or underburned. The method of the invention may be employed in the sintering of various materials, such as Portland cement raw material mixes, dolomite, magnesite, and the spent lime material produced in the paper industry and known as mesa, but since all the advantages of the new method are realized in its application to the production of cement clinker, the use of the method for that purpose Will be illustrated and described in detail.

It is well known that, in the production of Portland cement clinker, it is important that the degree, to which the clinker is burned, be kept within relatively narrow limits. In the burning operation, progressive chemical reactions take place and such reactions are necessary in order that the finished ground cement may have the desired properties of hardening and strength. The reactions are partly a function of the burning time and partly a func tion of rising burning temperatures and, as the reactions occur, the porosity of the material is progressively reduced. While the rate, at which the porosity decreases in relation to the reactions, may vary with different kinds of clinker, depending on the chemical composition of the clinker, the type of kiln used, and other factors, the porosity of the burned product is indicative of its quality. Heretofore, it has been common practice to control the degree of burning of cement clinker manually in accordance with variations in the porosity of the clinker as determined by variations in the weight of the clinker per unit volume. In so determining the clinker weight, a sample of the cooled clinker is taken at regular intervals of an hour or less and the pieces larger and smaller than selected sizes, as, for example, larger than 10 mm. and smaller than 5 mm., are discarded. A one-litre measuring vessel is then completely filled with the remaining pieces and the weight of the clinker required to fill the vessel and referred to as the litre weight is determined. In practice, it has been found that there is a reliable relation between the degree of sintering of the clinker and its litre Weight and that the harder the clinker is burned, the greater is its litre weight. While the litre Weight of a clinker may in many instances be a dependable basis for determining the quality of the clinker, the reliability of the control of the sintering process in response to variations in the litre weight of the clinker depends on the measurement of the litre Weight being carried on at regular and sufiiciently frequent intervals and on the adjustments of the burning process indicated as necessary by the litre Weight measurement being promptly made. The degree of sintering may vary considerably in a relatively short time, such as an hour, and, because of that, reliance on the determination of the litre weight of clinker as a basis for controlling the sintering process is not always safe.

The present invention is, accordingly, directed to the provision of a method for controlling sintering operations, which is devoid of the objectionable features of the prior method involving reliance on the litre weight of the sintered product. The new method makes use of the fact that, as certain materials are sintered, the resulting product varies in porosity inversely and in density directly with the degree of sintering and, in the practice of the method, pieces of the sintered product are caused to impinge upon an object which produces oscillations varying in intensity with the degree, to which the pieces were sintered. The oscillations are then converted into electrical signals, which may operate an indicator observable by the kiln operator and giving him a continuous indication, from which he can determine the appropriate adjustment of the conditions of the burning process, or, if preferred, the signals may produce a continuous record which may be observed by the kiln operator. Alternatively, the signals may be used to control any one or more of the factors involved in the sintering process. The signals may also be used to determine the destination of clinker burned to different degrees as such clinker issues from the kiln. The oscillations may be converted directly into electrical signals by means of an electrical pick-up or the conversion may be indirect with the oscillations producing sound waves which act upon a microphone.

In producing the oscillations, the pieces of the burned product are caused to have a free movement under the influence of gravity and the object producing the oscillations may be a wall confining the pieces in such movement. Such a wall may be part of a chute or trough, through which the sintered product is moving, or part of a cooler, such as a rotary or planetary cooler. Alternatively, the oscillations may be produced by impingement of the pieces of sintered material upon an object intercepting them in their movement and such an object may take the form. of a plate, a plurality of rods, etc. The contact of the pieces of the sintered material with one another in such movement also produces oscillations, to

which the devices converting the oscillations into electrion respective objects to produce oscillations which are then converted into separate sets of electrical signals. If desired, the movement of the sintered pieces producing the oscillations may be controlled so that a selected Weight of the pieces impinges upon the object in a unit of time. In another variation of the method, pieces of the sintered product are caused to impinge upon two different objects to cause them to oscillate with the pieces striking the respective objects differing in physical characteristics. Thus, the pieces striking one object may be those issuing from the kiln and of relatively high temperature, While the pieces striking the other object may be those issuing from a cooler and of relatively low temperature.

For a better understandingof the invention, reference may be made to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view in side elevation of part of a cement plant provided with means for practicing the method of the invention;

FIG. 2 is a sectional view through a part of the plant of FIG. 1 showing the use of a microphone in the practice of the invention;

FIG. 3 is a sectional view on the line 3-3 of FIG. 2;

FIG. 4 is a view similar to FIG. 3 showing an electrical pick-up used in the practice of the new method;

FIG. 5 is a fragmentary sectional view showing a FIG. 6 is a sectional view on the line 6--6 of FIG.

FIG. 7 is a view similar to FIG. 6 showing another form of the member, on which the pieces of clinker impinge;

FIG. 8 is a diagrammatic sectional view showing apparatus for the practice of the method of the invention, in which large and small pieces of clinker are separated from the remainder;

FiG. 9 is a view similar to FIG. 8 showing apparatus of a modified construction, in which oscillations of objects struck by pieces of clinker of two different sizes are utilized;

FIG. 10 is a diagrammatic sectional view showing an apparatus for practicing the method of the invention, in which a selected weight of pieces of burned material is caused to impinge upon an object per unit of time;

FIG. 11 is a schematic wiring diagram of one form of apparatus for practicing the method;

FIG. 12 is a graph obtained by the use of the invention;

FIG. 13 is a diagrammatic side elevational view of part of a plant for practicing one form of the method of the invention; and 7 FIG. 14 is a view similar to FIG. 13 of part of a plant for practicing another form of the method of the invention.

The installation shown in FIG. 1 includes a rotary kiln 26 having its lower end within a hood 21 mounted on the floor 220i the burners platform. A burner pipe 23 extends through the hood into the end of the kiln and is supplied with air by a fan, as is usual. The fuel used is coal dust contained in a bin 24 with a hopper bottom 24a and the coal dust flows from the bin through a pipe 25 into a measuring worm 26 connected by a pipe 27 to the burner pipe 23. The Worm is driven through a reduction gear 28 by a variable speed motor 29 controllable by an amplifying and relay device generally indicated at 30 and receiving energy through conductors 31.

The hot clinker issuing from the lower end of the kiln travels through the hood 21 and through an opening 22a in the floor 22 into a chute 32 leading to a cooler 33; The cooler is illustrated as of the reciprocating grate type but any suitable cooler, such as a rotary cooler, may be employed, if desired. The cooled clinker leaving the discharge end of the cooler travels through a chute 34 to a casing 35 containing a gate 36, by which the clinker may be directed into a compartment 37 or a compartment 38. V

In traveling through the chute 32, the hot pieces of clinker impinging upon the wall of the chute cause the wall to oscillate and a device 39 responsive to these oscillations may be mounted adjacent to the Wall. Similarly, the cooled pieces of clinker traveling through the chute 34 impinge upon the wall of the chute and produce oscillations, to which a device 40 mounted on or ad jacent to the wall responds. The devices 39, 40 may be a microphone and, in FIG. 2, a microphone 41 is shown mounted close to a wall of the chute 32 on a support 42. The microphone is preferably disposed within an enclosure 43 of sound-insulating material and it responds to the sound waves produced by the wall of the chute as the pieces impinge upon it.

The microphone 39 is shown as being connected to the amplifying and relay device 30 which controls the motor 29 and the microphone 40 is shown as being connected to a similar device 44 supplied with energy through a line 45 and controlling actuating means 46 for the gate 36. Such means may be a solenoid working against a spring or any other electrically controlled push-pull device, which can be operated to place the gate in either of its two positions.

It is to be understood that, in the practice of the invention, it is not essential that the devices 39 and'40 be placed at the locations indicated and both devices may air or Water.

be mounted adjacent to the chute 32 or on or adjacent to the chute 34, as desired. As the chute 32 is very hot, a device responsive to oscillations should not be mounted directly on the chute but the device may be placed close to the chute and protected against the heat by heat insulation or by keeping it cool by a flow of cool If the device is to be used to control the quality of the product, it is preferable to place the device adjacent to the chute 32, so that variations in quality will be ascertained as early as possible and corrective measures may be taken with the least delay. However, it is easier to make use of a device responding to oscillations produced by pieces of clinker, which have been cooled.

With the installation shown in FIG. 1, the electrical signals produced by the oscillations of the wall of chute 32 are employed to control the burning process by varying the rate, at which fuel is supplied to the kiln.. If

preferred, the signals may be used to control the rate at which the raw material is supplied to the kiln at its inlet and/ or the rate at which the kiln is rotated. Variations in the signals may thus be used to control the burning process automatically and the signals make it possible to keep the degree, to which the materials are sintered, within relatively narrow limits.

The signals produced by oscillations of the wall of chute 34 are employed in the installation shown in FIG..

to the wall of a chute 48, through which pieces of clinker are traveling. As the pieces impinge upon the wall, the pick-up device responds to the oscillations thereby produced.

Instead of utilizing the oscillation of the wall of a chute or trough, through which the pieces of clinker are traveling, the object, against which the pieces of clinker impinge, may be a plate 49, FIGS. 5 and 6, extending across the path of the clinker traveling through a chute or trough 50. The plate 49 is mounted on a rod 49a extending through an opening in the wall of the chute and into an electrical pick-up 51 on a fixed support 52. The opening through the wall of the chute may be defined by a flange lined with resilient packing 53 sealing the opening around the rod. If desired, the plate 49 may be replaced by a fork 54, FIG. 7, attached to a rod 54a extending into the pick-up device 51 through resilient packing 53' in an opening in the wall of the chute. The impinge-. ment upon the plate 49 or the tines of the fork 54 of the pieces of clinker traveling through the chute produces oscillations which are then converted into electrical signals and used for purposes previously described.

In some instances, it may beconvenient to make use stream is deflected by a gate 56 operable by a handle 57.

into a rotary screen 58 having an inner drum 59 with a coarse screen and an outer drum 60 with a fine screen. The pieces of clinker are directed into the inner screen and the pieces too coarse to pass through the openings of the screen'leave the screen through its lower end and return to the trough 55. The pieces passing through the openings in the inner screen fall upon the outer screen and the fine pieces passing through the openings in that screen drop back into the trough. The pieces of medium size leave the outer screen at its lower end and enter a chute 61, the lower end of which extends into an opening through the Wall of a chute 62, into which the trough 55 discharges. A microphone or pick-up 63 is mounted to respond to the oscillations set up in the chute 61 through which the medium size fraction of the clinker is passing. The opening in the wall of chute 62 is larger than the end of the chute 61 within the opening so that the oscillations of the chute 61 are not clamped by contact of the chute with the chute 62.

The arrangement shown in FIG. 9 is a modification of that shown in FIG. 8 and permits electrical signals to be obtained from oscillations produced by pieces of clinker of two different particle sizes. In the FIG. 9 construction, the pieces of clinker flowing through the trough 64 enter a rotary screen 65 and the oversize pieces leave the inner screen 66 and travel through a trough 67 to a chute 68, while the medium size pieces passing oif the outer screen 69 enter a chute 70. The fine pieces of clinker passing through the outer screen 69 enter the enlarged end of a chute 71 having a vertical extension 72 withopenings, through which theends of the chutes 68 and 70 project without making contact with the walls of the openings. A microphone or pick-up 73 is mounted to respond to the oscillations produced by the clinker impinging on the wall of chute 68 and a similar device 74 responds to the oscillations produced by the wall of the chute 70 under impingement by the pieces of clinker traveling therethrough.

In the construction shown in FIG. 10, a part of the clinker traveling through a vertical chute 75 is diverted by a flap 76 into a pipe 77 branching from the chute and extending downwardly and away from the chute. The pieces of clinker diverted into the pipe by the flap are discharged upon the belt of a weighing feeder 78 of conventional form, the feeder being connected through a chain 79 and an arm 80 to the flap to control the position thereof. With this arrangement, a constant weight of clinker per unit of time is discharged from the feeder and enters a chute 81 which leads back into the chute 75. An electrical pick-up or microphone 82 is mounted to respond to the oscillations of the wall of the chute 81 produced by the pieces of clinker impinged thereon upon discharge by the feeder.

In FIG. 11, there is shown a schematic wiring diagram, in which a microphone or an electrical pick-up is repre sented at 83, the device being connected by wires 84 to an amplifier 85 receiving energy through wires 86. The output of the amplifier is transmitted through conductors 87 and 88 to a milliarnmeter 89 and a recorder 90. The milliarnmeter provides a continuous indication of the intensity of the noise produced by the impingement of the traveling pieces of clinker upon a wall, for example, or upon an intercepting member, such as the plate 49, While the recorder gives a continuous record of the noise related to time.

In the graph forming FIG. 12, the curve 91 is representative of curves produced by a recorder 90 in the practice of the method. The abscissa of the curve is time measured in hours and the ordinate is the porosity of the product expressed in percentages. The curve, accordingly, shows the degree of sintering of the clinker measured in terms of porosity in dependence on time and it will be observed that, even within an interval as short as an hour, wide variations in the degree of sintering of the clinker may occur. The small circles on or near the curve are corresponding litre weight terminations made simultaneously hour by hour by the method heretofore used, the results being converted into porosity percentages. The results obtained in the difierent ways conform reasonably well. In the process from which the graph was made, a litre weight of about 1400 g./ltr. (or a porosity of 20%) was aimed at and, in practice, variations within the range of 1300 to 1500 g./ltr. are acceptable. From the graph, it Will be noted that, had the operator relied on the litre weight test alone, the results at the end of the first and second hours would have indicated satisfactory burning, whereas the continuous record shows that, within this period, adjustments in the burning process were required.

In the installation shown in FIG. 13, the oscillations of the wall of a chute, upon which pieces of traveling clinker impinge, are employed to control the rate of rotation of a kiln. For this purpose, the kiln 92 is provided with a toothed rim 93 encircling the kiln and meshing with a pinion 94 on a shaft 95 driven through a speed reducer 96 by a variable speed motor 97. The motor is controlled by an amplifying and relay device 98, which is similar to the'devices 30 and 44 and supplies energy to the motor received through conductors 99. The device acts in response to the oscillations of the wall of a chute 100, upon which traveling clinker impinges and which may correspond to either chute 32 or chute 34. A device 101, which may be a microphone or an electrical pick-up, responds to the oscillations and produces signals transmitted through the conductor 102 to thedevice 98. The difference in the signals varying with the differences in degree of sintering of the clinker are employed to vary the speed of rotation of the kiln by the motor 97 and thus control the burning operation.

In the plant shown in FIG. 14, the burning process is controlled by varying the rate of feed of the raw material to the kiln. The inlet end of the kiln 103 extends into a smoke chamber 104 connected by a flue 105 to the usual stack-and raw material in the form of slurry is fed into the inlet end of the kiln through a pipe 106, which extends through the smoke. chamber. A conventional slurry feeding device 107 is mounted on top of the smoke chamber and receives slurry through a pipe 108 and delivers it to the pipe 106. The feeding device includes 1 the usual paddle wheel, by which the slurry is fed at a rate depending on the rate of rotation of the wheel, and the device is also provided with an overflow pipe 109. The paddle wheel is rotated by a shaft 110 driven through a speed reducer 111 by a motor 112 and the rate of rotation of the motor is controlled by an amplifying and relay device 113, which is similar to the device 93 and supplies energy to the motor received through conductors 114. The device 113 acts in response to the oscillations of the Wall of a chute 115, which may correspond to either chute 32 or chute 34. A device 116, which may be a microphone or electrical pick-up, responds to the oscillations and produces signals varying with the degree of sintering of the clinker and transmitted to the device 113 through the conductor 117 to cause the device to vary the feed of raw material to the kiln in accordance with differences in the degree of sintering of the clinker.

I claim:

1. A method of sintering material in a kiln or the like, which comprises continuously discharging the sintered product in pieces from the kiln, causing free movement of the sintered pieces by gravity with the pieces impinging in such movement upon an object and thereby causing the object to oscillate, and converting the oscillations of the object into electrical signals which vary with differences in the degree of sintering of the product, and controlling the degree of sintering of the material by such electrical signals.

2. The method of claim 1, which includes converting the1 oscillations of the object directly into electrical signa s.

3. The method of claim 1, in which the oscillations of the object produce sound waves and intercepting and converting the sound waves into electrical signals.

4. The method of claim 1, which includes impinging the sintered pieces upon a wall in their movement.

5. The method of claim 1, which includes interposing the object in the path of movement of the sintered pieces.

6. The method of claim 1, which includes moving the sintered pieces freely as soon as they leave the kiln.

7. The method of claim 1, which includes cooling the sintered pieces and impinging the cooled pieces upon the object.

8. The method of claim 1, which includes supplying fuel to the kiln at varying rates and controlling the fuel supplying means by said electrical signals for the purpose of keeping the degree of sintering of the kiln product Within selected limits.

9. The method of claim 1 which'includes supplying to the kiln at varying rates the material to be burned therein and controlling the material supplying means by said electrical signals for the purpose of keeping the degree of sintering of the kiln product within selected limits. i

10, The method of claim 1, which includes rotating the kiln at varying speeds and controlling the rotation of the kiln by said electrical signals forthe purpose of keeping the degree of sintering of the kiln product within selected limits. 7

11. The method of claim 1, which includes separating the sintered pieces into fractions of different 'sizes and impinging the pieces of a single fraction upon the object 16. The method of claim 1, which includes controlling the movement of the sintered pieces to cause a selected weight of the pieces to impinge upon the object in a unit of time. e

17. The method of: claim 1, in which the material being sintered in a member of the class consisting of a pieces, and classifying said cooled pieces of material by such second-mentioned electrical signals.

20. In the sintering of material in a kiln or the like,

i the steps which comprise discharging the sintered pieces to produce oscillations, which are converted into electrical 1 signals.

12. The method of claim 11, which includes impinging separate fractions on respective objects to produce oscillations, and converting said oscillations into separate sets of electrical signals.

13. The method of claim 1, which includes impinging pieces of the sintered product of different physical characteristics upon two diileren t objects to cause the objects to oscillate.

14. The method of claim 13, in which the piece striking the difie-rent objects differ in temperature.

15. The method of claim 13, in which the pieces strikinig the different objects differ in size.

from the kiln, causing the discharged panticles to impinge against an object and thereby causing the object to oscillate, converting the oscillations of the object into electrical signals which vary with differences in the degree of sintering of the product, and utilizing the electrical signals to classify said pieces of material.

References Cited in the file of this patent UNITED STATES PATENTS 3,011,634 Hutter et a1. Dec. 5, 1961 3,029,943 Diamond et al. Apr. 17, 1962 FOREIGN PATENTS 604,916 France May 17, 1926 

1. A METHOD OF SINTERING MATERIAL IN A KILN OR THE LIKE, WHICH COMPRISES CONTINOUSLY DISCHARGING THE SINTERED PRODUCT IN PIECES FRO THE KILN, CAUSING FREE MOVEMENT OF THE SINTERED PIECES BY GRAVITY WITH TTHE PIECES IMPINGING IN SUCH MOVEMENT UPON AN OBJECT AND THEREBY CAUSING THE OBJECT TO OSCILLATE, AND CONVERTING THE OSCILLATIONS OF THE OBJECT INTO ELECTRICAL SIGNALS WHICH VARY WITH DIFFERENCES IN THE DEGREE OF SINTERING OF THE PRODUCT, AND CONTROLLING THE DEGREE OF SINTERING OF THE MATERIAL BY SUCH ELECTRICAL SIGNALS. 